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Re: [PATCH] nested partitions

From: Bruce Dubbs
Subject: Re: [PATCH] nested partitions
Date: Sun, 24 Jan 2010 18:38:40 -0600
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv: Gecko/20080722 SeaMonkey/1.1.11

Robert Millan wrote:
On Fri, Jan 22, 2010 at 07:03:21PM +0100, Vladimir 'φ-coder/phcoder' Serbinenko 

Partition types are easily screwed. Why not just check for the presence
of the label?

I have a feeling I already explained this somewhere.  Doesn't seem to be in
this thread, maybe on IRC?  Anyway, it won't hurt to ellaborate on it...

First of all, the whole label type proliferation problem is inherently
impossible to resolve by technical means.  Labels overlap each other,
they can coexist without any garantee that the user expects them to be
there at all or include meaningful data.

There is a fairly long thread at util-linux-ng that discusses this problem in the context of very slow and very small devices. It starts approximately at

The ultimate solution was to not search for multiple partition type signatures on small devices.

You *can't* reliably check for any partition label.


So instead of supporting things like:


  (ambigous; what does this mean in an hybrid MSDOS/GPT ?  What about other
  hybrid schemes?  GRUB can't tell!)

... we could support:


whose meaning is pretty clear.  Then the user can nest as much as they like,
but they will also have to deal with the problem of identifiing the labels.

I like this idea, but wonder if it would be useful to have something like (grub drive, partition type, filesystem type) for each partition to consider. For example:


Minix: (hd0,msdos1,msdos1)

Solaris: (hd0,msdos2,sun1)

*BSD: (hd0,msdos3,bsd1)

With this approach, the burden is no longer in GRUB.  Then I don't care
how weird disk layouts can become, because GRUB doesn't have to probe
them.  We can even support things like this if it makes users happy:


Can you translate that.  I don't understand.

  -- Bruce

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